Generally, the hydraulic excavator as the construction machine is configured of a self-propelled lower traveling body, an upper revolving body that is rotatably mounted on the lower traveling body and a front device that is provided on the upper revolving body so as to be capable of moving upward/downward.
The upper revolving body is configured of a revolving frame that forms a support structure body, a counterweight that is provided on the rear side of the revolving frame so as to extend in a left-right direction of the revolving frame and keeps weight balance with the front device, an engine that is located on the front side of the counterweight and is mounted on the revolving frame in a horizontally installed state extending in the left-right direction, a cooling fan that is provided on one side in the left-right direction of the engine and, rotates using the engine as a power source and thereby sucks external air as cooling air, a heat exchanger such as a radiator, an oil cooler and the like that is located closer to an upstream side of a flowing direction of the cooling air than the cooling fan, is provided so as to face the cooling fan and cools a fluid with the cooling air and an exterior cover that includes a side surface cover part that faces the heat exchanger in the flowing direction of the cooling air and is equipped with external air inlet ports and atop surface cover part that covers the upper sides of the engine, and the heat exchanger.
A diesel engine is used as the engine of the hydraulic excavator. It is said that this diesel engine emits a large amount of nitrogen oxides (hereinafter, refer as NOx) and the like. Thus, there is a NOx purifying device adapted to purify NOx as a post-treatment device for the exhaust gas from the diesel engine. This NOx purifying device is configured of, for example, a urea water selective reduction catalyst that is provided in an exhaust pipe of the engine and removes the nitrogen oxides in the exhaust gas and a urea water injection valve that injects the urea water solution (hereinafter, refer as urea water) as a reducing agent to the upstream side of the urea water selective reduction catalyst. Thereby, a urea water tank adapted to store the urea water that is the reducing agent is provided on the hydraulic excavator that is equipped with the exhaust gas post-treatment device for the exhaust gas.
Here, there are small-type hydraulic excavators called an ultra-small revolving type, and a rearward ultra-small revolving type that are suited for work in a narrow work site in recent hydraulic excavators. In these small revolving type hydraulic excavators, an upper revolving body is miniaturized in such a manner that the upper revolving body is able to substantially revolve in a vehicle width of a lower traveling body thereof.
Therefore, since an installation space on the revolving frame is reduced in the small revolving-type small-type hydraulic excavator, apart on the revolving frame is brought into a state of being very congested with various kinds of devices. On the other hand, it becomes necessary for the urea water tank to have a large capacity that allows sufficient storage of the urea water. In addition, it is necessary to install the urea water tank at a position within easy reach from the outside so as to make performance easily of water supply work possible. Further, since the urea water is liable to deteriorate when a temperature rises above, for example, 60° C., it is desirable to install the urea water tank on a place that is spaced a part from the engine and the like that is the heat source and where air flows.
Accordingly, in the hydraulic excavator according to Patent Document 1, it is configured such that a heat exchanger upstream room that is located on the upstream side of the cooling air flowing direction of the heat exchanger and is surrounded by the revolving frame, the heat exchanger, the counterweight, the exterior cover is provided and the urea water tank is disposed in this heat exchanger upstream room.